'archtreasurer' originates from English, formed by the prefix 'arch-' (from Greek 'arkhē/arkhos' via Latin/Old French use) meaning 'chief, principal' plus 'treasurer' (from Old French 'tresorier' and Late Latin 'thesaurarius').

'treasurer' comes from Late Latin 'thesaurarius' (from Greek 'thēsauros' meaning 'treasure'), passed into Old French as 'tresorier' and into Middle English as 'treasurer'/'tresourer'; the prefix 'arch-' (from Greek 'arkhos' meaning 'ruler, chief') was attached in English to form 'arch-' + 'treasurer', yielding 'archtreasurer' to denote the chief officer in charge of a treasury.

Initially a compound literally meaning 'chief treasurer' and historically used to denote the top treasury official; the meaning has remained essentially the same as 'principal treasurer' in modern usage (now rare/archaic).